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 July 15, 2005
The NuForce Revolution: Reference 8b Mono Amplifier Premonition "The revolution has begun," the caller warned. "We have reached critical mass. Don’t be left out." "What revolution? What mass? Who is this?" "A friend of Jason’s. The new force is with us." The line went dead. I fell back into the pillow, staring at the ceiling. My mind is no stranger to the paranormal. Had I been dreaming? I drifted into reverie. The name "Jason" came from reading too many spy novels. The notion of a force, new or otherwise, was a popular movie device. When the caller said "us," did he mean some league of extraordinary gentlemen that appealed to my adolescent side? I’m of a pioneering bent, and the word revolution had struck my fancy. I pondered its meaning. If forces for change were afoot, I would hate to be late to the Bastille. A few days later, I received an e-mail thanking me for a 2005 Consumer Electronics Show 2005 Jimmy Award. The note was from a company called NuForce. The writer was Jason Lim. After recapping my visit to the NuForce exhibit, Jason mentioned that his company had already shipped dozens of units of its "digital" amplifier to Sweden. The uprising had begun, and Stockholm was ground zero. If dreams portend, I had seen this adventure coming. Early warning signal My first exposure to this evolutionary, if not revolutionary, amplifier design took place in Minneapolis in September 2003, on a visit to Bel Canto Design’s headquarters. Company president John Stronczer swore me to secrecy, but now, with company approval, I can tell you that Stronczer’s secret was a prototype Bel Canto eVo amplifier with an uncommon power supply that dispensed with a power transformer and its accoutrements. At a skunkworks a few blocks from the factory, John treated me to a brief but exhilarating demonstration of amplification to come. Devoid of chassis and power transformer, Bel Canto’s nascent amplifier consisted of circuit boards and cable harnesses stuck together at strange angles. In looked like a robot fetus whose neurons were connected to a CD player and a pair of bookshelf loudspeakers. The opening notes of Miles Davis’ "So What" floated before my ears with unprecedented clarity and dynamic contrast. "What am I hearing?" I asked Stronczer in discombobulated disbelief. "It’s what you’re not hearing," he replied. "There’s no 60Hz transformer noise riding on the signal. We’ve gotten so used to the sound of a transformer in the circuit that we don’t notice its presence until it’s gone." Stronczer then explained about the switch-mode power supply (SMPS) alternative to the transformer-based linear power supply, which has motivated stereo amplifiers since time immemorial. He pointed out that the SMPS was nothing new -- off-the-shelf models are in everyday use powering our personal computers. However, he considered such devices jagged, noisy, little pills unsuitable for use in high fidelity, and so had created a secret lab to design and test a proprietary SMPS. Although stories of flying resistors and shocked fingers were still fresh at the lab, a breakthrough SMPS had been developed. It was only a matter of time before Bel Canto’s sweet little amplifier hit the market. ICEpower to the fore Obsessed with the sound I’d heard in Minneapolis, I began to investigate the state of transformerless "digital" amplifiers. To my surprise, the Jeff Rowland Design Group, builders of classic solid-state muscle amps, had already introduced a lightweight design, the Model 201, which used ICEpower, a power-conversion technology licensed from Bang & Olufsen. Included in the B&O module was a switch-mode power supply. Although I was eager to try the Rowland amp, rumor had it that the 201 had two flaws: 1) it wasn’t designed to handle power surges and the other mains anomalies that are plentiful in Central America, where I live; and 2) the 201’s SMPS was a bit basic for hi-fi use, and would probably be improved on in a second generation. Thus, to this day, I have sadly abjured the privilege of auditioning a Jeff Rowland Model 201 in my system. A new force in amplification I’d hoped to hear Bel Canto’s new amplifier with proprietary SMPS during the 2005 CES and was disappointed when it didn’t show. However, I did find a compelling substitute from an unexpected source. At the Alexis Park Hotel, Jason Lim and Casey Ng -- respectively CEO and VP of product development of NuForce, based in San Jose, California -- unveiled a pair of tiny monaural amplifiers that used proprietary analog modulation designed by their CTO, Tranh Nguyen. The Reference 8 ($1600/pair USD) produced an edgeless 70W of solid-state power. In the presence of the beguiling NuForce amps, I felt like Steven Stills: If you can’t be with the one you love, love the one you’re with. I was smitten. Little did I realize that I would eventually test not just one, two, or even three NuForce Reference 8s, but, counting a recent modification, five slightly different-sounding units. This article describes three months of listening to a most beguiling baby of an amplifier go through its teething stages. Bundle of joy The bundle from San Jose, California arrived in San Jose, Costa Rica at 10 a.m. The unlikely stork was a slightly built deliveryman who tucked the carton under one arm while handing me papers to sign. Expecting from NuForce a pair of monoblocks, my heart sank. A chassis seemed to be missing. I signed for the box while asking about a second. The stork shrugged. He knew nothing of a delayed twin. Slicing through the custom inspector’s red tape (how appropriate), I opened the package to behold, under a layer of insulation, two small boxes covered in bubble wrap. Each box contained a plastic bag, inside of which was a metal box. A flick of the wrist and I was grasping a 2.5-pound chassis in my bare hand. Unwrapping an amplifier had never been so easy. Both channels of the Reference 8 had arrived intact. I was the proud papito of twins. Installation issues The NuForce Reference 8’s near-weightlessness creates problems of ergonomics: beefy AC cords, anaconda-sized speaker cables, and unwieldy interconnects pull the amps right off the shelf. Tightening the binding posts would send the chassis sliding. I resorted to placing heavy blocks of almond wood atop each channel, taking care not to block the air slots. As the Reference 8 gains popularity, it may behoove me to market almond blocks as sound-enhancing amplifier anchors. At least they didn’t harm the sound. Power cords had a notable effect on the Reference 8’s tonality and imaging. The pair of channels had arrived without their stock power cords, but I wouldn’t have used them anyway. I soon learned that my usual thumb-thick, 9-gauge cords were too heavy, both physically and sonically, for the nimble Ref. 8. I settled on DIY cords of helical OCC-copper speaker wire. The almond blocks held fast. Loudspeaker cables, to my ear, did not affect the Reference 8’s performance as much as did AC cords and interconnects. Perhaps the amplifier’s high damping factor, low output impedance, and phase behavior negated to some degree the influence of speaker cables. When one of my Taiwanese speaker-cable pythons came apart at the spade from dangling too heavily from a binding post, I substituted two braided DIY cables that gave away frequency extremes to the snakes but were otherwise most acceptable. I’m not certain, but NuForce owners might save money by buying speaker cables by the pound (less is more!) rather than by reputation. Because the Ref. 8’s on/off switch is around back, easy access to the rear panel is important. Although I left the amps powered up all the time, I would hesitate to house the amplifier in a rack or bookcase whose rear I couldn’t easily reach. Finally, the blinding blue LED on the face of each monoblock needs addressing. To block the glare, I placed rolls of black felt in front of each faceplate, inadvertently creating a magic show. Anyone listening to my Reference 8s for the first time soon notices that my Audio Research VM220 power amp isn’t aglow. When asked where the amplifier is, I unblock the view of the blue LEDs. Inevitably, a murmur of amazement follows the unveiling. I feel like the Wizard of Odd. Original Reference 8 For five weeks, I lived with the original CES version of the NuForce Reference 8. The experience was a happy one. Hooked up to my regular electronics (Theta Digital Carmen transport, Audio Aero Prima DAC 24/192 Mk. II, and Audio Research Reference 3), the amplifier displayed a grain-free clarity that rivaled single-ended triode amplifiers. The frequency response was whole-cloth -- no tonal bulges or dips stood out. Best of all, bass control was load-independent; the Reference 8 could handle any loudspeaker on the premises, including the Focal-JMlab Diva Utopia Be, Paradigm Signature 8, and Usher CP-6391. Of mild disappointment was my discovery that the Ref. 8s’ 140W output (the outputs of both amps summed) sounded less powerful than the 44W produced by my beloved SET amplifier. Of course, the energy-inefficient SET amp weighs 120 pounds, runs blister-hot, and costs more than $9000. The low-consumption Reference 8 weighs mere ounces, barely warms the fingertips, and costs $1600/pair. The comparison was instructive. Although I preferred the SET amp’s slightly greater image density, "weighing" the advantages of the NuForce for use with 90dB-sensitive dynamic speakers favored the solid-state amp by a wide margin. But even 70W can be less than necessary. Although the NuForce website states that "there is no clipping at [the Reference 8’s] rated 140W," I found that the original unit’s 70W could be consumed rather dramatically. About seven minutes into "Stimela," from Hugh Masekela’s CD Hope [Triloka KAT 2020-2], the proceedings swell to rollicking live-performance levels -- great fun! Fed a stream of raging amplitudes for a minute or so, the little NuForce suffered indigestion, and a series of clicks emanated from the Diva Utopias. Luckily, I was holding the remote control in hand against just such an occurrence. Although the system wasn’t damaged, I decided to save Masekela for a bigger amp. Reference 8 Revised Though I never mentioned the clipping incident to Jason Lim of NuForce, I was relieved when he sent me a more powerful Reference 8 in March. This amp, which I call the Reference 8 Revised, was rated at 100W, which should have been enough oomph to play "Stimela" all the way through without blowing a driver. Unfortunately, an issue arose. The original 70W amplifier had a fixed gain of 26dB, which meant that for an indicated volume setting on the preamplifier, I could expect a certain loudness level at the listening position. The Reference 8 Revised came with a fixed gain of only 23dB, which required me to recalibrate the gain control for a desired output. Unaware of the lower sensitivity, my immediate impression was that the new 100W amplifier was dynamically constricted (i.e., a wimp). In truth, I was simply listening at a lower volume level but didn’t know it. Because any doubling of power equals a 3dB increase in gain, by going the other way, from 26dB to 23dB of gain, it sounded as if I was listening to a 35W amplifier. I advised Jason Lim of the situation and he wrote back to tell me that Tranh Nguyen (who had been a chief power-supply designer for the US-made Tomahawk missile) had erred. After lowering the gain of the "modulator" for better performance, he had forgotten to compensate for the change in sensitivity by adjusting the input buffer gain upward. Although this explanation should have encouraged me to increase volume-level settings for the customary test CDs (I misspend my life listening to the same tracks over and over), I could never get the hang of it. Consequently, despite knowing better, my evaluation of the Reference 8 Revised was psychologically impaired. The Reference 8 Revised did come with two blessings, however. First, the individual binding posts were replaced by a Cardas Cable wheel lock. This screw-down, one-piece connector enables one to make tight, efficient cable hookup using bare hands. Cool. The second benefit was the inclusion of feather-light power cords specially designed and built by Stealth Audio. The optional Stealth power cord sells for $480, which by Stealth standards is practically disposable. The only problem was that the combination of Reference 8 Revised and Stealth sounded thin in the lower midrange. Even my big-booty DIY cord lacked heft. Perhaps the unaccustomed gain levels were at fault, but the issue was soon moot. After an exchange of e-mails, Lim agreed to send a Reference 8 with 100W and 26dB of gain. There’s nothing more heartwarming than a manufacturer who responds to feedback. Reference 8 A pair of Reference 8s with the latest specifications arrived at the beginning of April. According to the factory, the present production model includes upgrades to the SMPS (no further details offered), higher-grade capacitors, and silver hookup wires. The amplifier’s speed of attack is said to have increased, like a home-run hitter’s bat speed, and the extra quickness to produce even more power. Having lost the use of my DIY AC cables, I installed the NuForces using mismatched power cords. That is, I hooked up one channel with 10-gauge cable and the other one with 11-gauge. What a mess! The phasing was off, the soundstage leaned to one side, and bass had a life of its own. I will never again try this at home. Replacing the fat cords with the svelte Stealths proved a blessing. Now these bespoke cords proved their worth. The upper bass was full, the midrange bloomed with color, and the soundfield expanded well past the speakers’ outer edges. At last, the amp/cord combination had lived up to my high expectations. The biggest improvement in the gain-adjusted Reference 8 was a sense of unlimited forcefulness aspiring to burst forth. I was never afraid to crank up the amplifier with Hugh Masekela or another explosive performer on tap. I imagine there is a clipping point somewhere up there in volume heaven, but I didn’t have the guts to find it. Although the 100W Reference 8 amplifier did not produce deeper bass than the 70W original, giving in to the temptation to crank up the amp resulted in amazing low-frequency displays. For example, the synthesizer beat on track 9 of JMlab’s Test CD No.6 masks a sustained deep-bass riff that can’t be detected at 76dB. At 90dB, the bass has the sinister presence of a Pink Floyd heartbeat. The original Ref. 8 may have been capable of inducing similar dread, but I lacked the desire to push the 70-watter hard enough to prove it. With the new amplifier’s high gain and high power, it was time to get careful with that axe, Eugene, and set the controls for the heart of the sun. Reference 8b Finally, we reach the subject of this essay. Weeks of testing each variation of the Reference 8 set the groundwork for the arrival of a second "finalized" production model, the NuForce Reference 8b (b for balanced). Physically, the Ref. 8b is the same as the 8, except that it’s a few ounces heavier, has a more elegant faceplate, and replaces the 8’s RCA inputs with XLRs. Unlike some amplifiers with XLRs, the Reference 8b is truly balanced. (So, too, is the Reference 8, despite its single-ended inputs.) Whereas the 8b has both + and – phases connected, the 8 leaves the negative input unconnected to accommodate the RCA connectors. Thus the voltage swing in single-ended configuration is half that of the balanced edition. Theoretically, the main difference is that the Reference 8b will play significantly louder with a truly balanced preamp. In practice, the 8b sounded a tad cleaner and clearer, as well as more powerful, than the 8. This was true using a preamp that was not fully balanced. Perhaps my "balanced" interconnects are better analog conductors than the single-ended cables I used with the Reference 8. Anything is possible. With a truly balanced preamplifier such as the Audio Research Reference 3, the 8b is a powerhouse to rival classic muscle amps of the past and present. The sense of undistorted power is like listening to a +300W amplifier with input transformer and traditional power supply. The ARC/NuForce combination is an extrovert’s delight. Too bad it’s an unlikely pairing given the discrepancy in price. Hard to Imagine someone in the market for a sub-$2k amplifier would spend $10,000 on line stage. But assuming one would, wow! Despite the awesome capabilities of the ARC Reference 3, I decided in the interest of fiscal sanity to test the Reference 8b without any preamp at all. My digital processor, the Audio Aero Prima D/A Converter 24/192 Mk. II, has balanced outputs and a "high-precision buffer and volume control" that allows me to skip a stage of amplification as well as a pair of interconnects. Listening to the 8b via the Prima DAC’s balanced outputs without intervening devices was instructive. First, it shows that the absence of power-transformer noise takes more aural adjustment than I originally thought. At low volume levels, the sound was harmonically thinner than with a linear amp. In order to bring into audibility true lows, as opposed to transformer-enhanced frequencies, the volume had to be raised slightly higher than usual. Too much gain, however, and newly revealed recording artifacts became distracting. As I found with amplifiers that use the Tripath module, the volume range in which the music locks in with the NuForce seemed to be narrower than with traditional amplifiers. Secondly, despite the excellence of the Prima DAC’s output buffer, using a tube preamp with the Reference 8b is a luxury worth having. With the ARC Reference 3 installed, the music was more romantic, the soundstage more dimensional. Without the ARC, the presentation was more cerebral, the imaging tightly focused. My preference is to use the Reference 3. A friend who owns the Reference 8 attests that the Audio Research SP16L (tubed) is an excellent match for the single-ended Reference 8. In order to test the 8b with a more proportionally priced balanced tube preamp, I am bringing in an ARC LS16 Mk II, which at $3500 almost makes sense. Sound of music The NuForce Reference 8b sounded, in a word, new. That is, I don’t recall having heard another amplifier whose sound foreshadowed the musical immediacy of these little monaural blocks. The closest antecedent in my experience would be the mighty Halcro dm68, which also uses a switch-mode power supply. Of course, the Halcro’s level of distortion, almost immeasurably low, let me hear low-level lyrics and musical filigrees that eluded the Reference 8b’s resolving abilities. To my ear, however, the tiny Reference 8b had more warmth of tone than the big Halcro. Unless one is listening on the edge of one’s chair, the comparison favored the NuForce for most music. In comparison to past models from the big-gun manufacturers of solid-state amplifiers, the NuForce Reference 8b was the king of melody. Its amplitude and timing induced physical reactions I have seldom experienced in my demo room. Within seconds of the first bars of music, listener after listener began to perk up. Their eyes widened, and they leaned forward as if to catch notes floating on the breeze. If the music was bouncy, they smiled. If there was angst, they pursed their lips. The Reference 8b excelled at communicating the interplay of musical ideas, whether among jazz players or choral singers. Invariably, their eyes moved as they "saw" performers suddenly emerge from various planes between and behind the loudspeakers. I have yet to see a slump of boredom or indifference from anyone who has listened to the NuForce (but see below). At the conclusion of the first track, invitees usually go over to inspect the monoblocks. Invariably, they express amazement that such big, glorious sound could come from such miniature operatives. I love it when that happens. Underpinning the Reference 8b’s melodic expression was a robust bass response that warmed the midrange, pushed the pace, and endowed the setting with ambience, whether real or a figment of the mastering engineer’s imagination. For instance, the opening of the Dave Matthews Band’s "Oh," from Some Devil [RCA C3GZ2], contains a swirl of percussive effects. Through the Reference 8b, the drum kit was arrayed in a circle that stretched from channel to channel, the directional cues enhanced by the retrieval of note plus echo. As Bob Trump of TG Audio once said, "Bass makes space." The Reference 8b made space extremely well. Besides enhancing soundfield activity, the Reference 8b’s hearty bass contributed to a palette of tonal colors that elude most solid-state amplifiers. For instance, some amplifiers capture the gamma of certain instruments, like acoustic guitar, but sound bleached on others, such as the trumpet. The Reference 8b did breathtaking trumpet, reminding me of the magnificent VIVA Solista SET amp. I attribute the 8b’s richness to its bass response because of a recent comparison to a prototype ICEpower amplifier with switched-mode power supply. The ICEpower amp excelled in high-frequency definition and extension, but as the scale descended, its tone became drier, its retrieval of ambience less dramatic. A dealer pal who heard the comparison summed it up, accurately I think: the Reference 8b had more guts. Contrary opinion Although I consider the NuForce Reference 8 a groundbreaking product and the state of a new audio art, I must relate an experience that at first gave me a few days’ pause. Carlos, one of my good friends, is a longtime audiophile with a blue-chip stereo system. When I invited him over to hear a terrific new loudspeaker, the Usher Audio CP-6391, I assumed he would like the sound based on a sonic memory of other great speakers that have come through here on their way to their rightful owners. How wrong I was. After comparing versions of Ariel Ramirez’s Misa Criolla, Carlos asked to hear Patricia Barber’s Café Blue [Premonition/Blue Note 737-2, FIM Re-Master CD010]. I cued up track 9 and Carlos began to fidget and shake his head. Normally a mild-mannered gentleman, Carlos began to react to the sound with growing antagonism. "No, no, no," he said. "There’s something terribly wrong with the sound!" I asked what it was. He said that the timbre was wrong, harmonics were missing, and the lyrics were incomprehensible. I agreed, but attributed the shortcomings to the recording, which I dislike intensely. Carlos volunteered that he had heard great as well as mediocre sound in my home over the years, but never, until that moment, had he heard bad sound. He was quick to add that he did not think the loudspeakers were at fault. He pointed a metaphorical finger at the NuForce amplifier. Carlos then suggested that I spend too much time in isolation and needed to come over to his house to recalibrate my ears with the sound of real music. Although I agreed that I needed to get out more, I did not think Carlos’s suggestion would modify my appreciation of the NuForce. Instead, I wondered whether Carlos was suffering a reaction to the sound of something missing: i.e., a transformer-based power supply. In the absence of line and transformer noise, Carlos may have lost his bearings, which caused a stress-filled response. I mentioned this episode to the people at NuForce, to see if anyone else had reported a polarized reaction to their product. Not yet, they said. Although Carlos’s experience may be uncommon, there remains a chance that owners of traditional amplifiers may not cotton to the sound of the NuForce and other designs that use a switched-mode power supply. A friend of mine has remarked that an SMPS takes some getting used to, but that afterward there’s no going back to a linear amp. Perhaps owners of mammoth muscle amps may never choose to sample the effects of SMPS. Cons
Also, at 100W, the Reference 8b lacks power compared to other so-called digital amplifiers -- or does it? I understand that the 1000W ICEpower module produces only a tenth of that under certain conditions. At any rate, bragging rights nowadays require big numbers, especially since several "chip-amp" manufacturers are warning of tons of low-cost power in the near future. Conclusion The forces at NuForce are aware of the limitations of their debut amplifier and will gradually improve its specifications as well as the pickiest listening results. However, in comparison to today’s alternatives, the Reference 8b stands out as a brilliant new departure. Its small size, low price, and full-bodied performance have inspired aficionados to call its implementation "revolutionary," though NuForce has never adopted the term. I consider the Reference 8b a standard-setter equal to the Mark Levinson ML2 of the 1970s or the Bel Canto eVo2 of the 1990s. When recently asked to say something quotable about the NuForce amp, I replied, with heartfelt expression, "Hail to a new star in the hi-fi firmament! May the NuForce be with you." Despite the sci-fi patois, the sentiment deserves affirmation and I own up to it. I hereby join the revolution. Vive la NuForce! …Jim Saxon Manufacturer contact information: NuForce E-mail: salesteam@nuforce.com
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My main criticism of the
NuForce Reference 8b is that it simplified the music a wee bit, particularly in the high
frequencies. On large-scale orchestral pieces, crescendos of massed strings tended to be
rounded off more than they should have been. On the smaller-scale music I prefer, the
Reference 8b did not supply Halcro or even ICEpower standards of microdynamics and
high-frequency shimmer. But I’m talking absolutes here. Had I never heard the Halcro
or ICEpower, I would never have known better. 